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Severe flatfoot-Should we treat with SMO or Insole?

July 28, 2020


Severe flatfoot-Should we treat with SMO or Insole?

July 28, 2020

We are aware of different orthotic treatment existing for severely pronated foot [severe flat foot]. after treating a large group of patients aged between 3 years to 15 years, we have stopped providing regular foot orthotics with 3-point correction principle for candidates with moderate to severe talar displacement and switched completely to Supra-Malleolar Orthosis [SMO]. This treatment method gave a satisfactory outcome in the majority cases and achieved excellent correction after using few months together with good physical training.


SMO General Description        

SMO is the acronym for Supra-Malleolar Orthosis and it gets its name for the part of the body for which it encompasses. This orthosis supports the foot until just above the anklebones or malleoli. SMO is considered the shortest of the Ankle Foot Orthosis [A.F.O]

Who would get benefit with SMO treatment?

Patients with severe flat feet [Pes planus], Flat foot with heel valgus [Pes plano-valgus] or hyper-pronated foot. The other conditions include hypotonia, tri-planar instability in weight-bearing, inability to stand independently, mild toe-walking, developmental delay, delay in acquiring gross motor skills, poor coordination or balance.

The orthosis works well if the talar displacement is correctable passively. The best age to start is 3 yrs onward until approx. 15 yrs aged. We have also used rarely to some patients aged more than 15 years as an option to contain the existing deformity


Patients should not get fitted SMO if they have;

  1. Calf or TA contracture (does not allow the calcaneus to settle down to create a sterope to uplift the talus and let it re-position)
  2. Age below 3 yrs (tarsal bones are too tiny and the articulating space between the calcaneus and talus is a lot to form the sterope that uplift the talus and let it re-position). This may ultimately lead to only squeezing of the soft tissue, which indeed will lead to strong bruises or pressure marks
  3. Conditions with Neurological involvement (eg: cerebral palsy)
  4. Severe spasticity

Ring Closure Concept and SMO Construction

The subtalar circular ring closure concept was first developed in 1994 by Dr.Monique Baise and Kurt Pohlig in Germany. A combination of laminated carbon fiber outer shell together with soft inner leather boot creates a ring external shell at the mid-foot and provides an external arthrodesis at talo-navicular, subtalar and calcaneal-cuboid joints. it also re-position and stabilizes the Talus bone.

If the child is less than 10 kg of body weight, we also use Polypropylene [PP] instead of carbon lamination since the weight-bearing tolerance is minimal in PP material.


SMO Treatment Goal

The primary goal is to help the patient to improve the walking and standing balance by maintaining vertical talus and neutral heel while maintaining 3 arches of the foot. Repositioning the bone structure enable the foot and ankle muscles to work in correct bio mechanical directions. This will also reduce muscle fatigue.

Movements in the proper foot and ankle bio mechanics strengthens the muscles and tendon, to hold the joints structure in the future even without a brace.

Treatment Period 

The expected period of use is between 2-5 years. however, it may vary according to the individual medical conditions and improvements. The doctor recommends using the orthosis until the Talus can hold itself in position with the help of supporting muscles

Patient Journey

An initial consultation by an orthopedic specialist with diagnosis and prescription is mandatory before seen by an orthotist for SMO. A multidisciplinary team including treating physician, orthotist and physiotherapist are involved in the whole course of treatment. The patient should have initial X-Ray in standing (2 planes – transverse and medial sagittal) before the visit to orthotist.

The orthotic journey starts with measurement by corrective cast [repositioning the talus with plantarflexed foot and inversion]

Once the orthosis is manufactured, the first trial of the soft inner leather boot is done followed by the final fitting of the laminated shell. A control X-Ray is suggested to see if the device giving the desired correction. The control X-ray should be taken in standing position with orthosis on.

The difference is compared by drawing lines that represent the axis running through the mid of the talus, aligns with the axis running mid of the 1st Metatarsal

Minimum of 4 follow-ups are recommended (1st – in 2 weeks, 2nd – 4 weeks, 3rd – in 6 months and 4th – after 12 months)


Starting with an SMO

An initial wearing guideline to be followed upon final fitting. It is normal to have some red marks on the patient’s foot after wearing the orthosis because of corrective pressure from the orthosis and it should disappear within 20-30 minutes. If the red marks stay beyond 30 minutes, then patient/parent has to communicate with orthotist to make further adjustments.

The child should always wear SMO with socks and shoes. The best types of shoes to accommodate SMO’s are basic gym shoes with laces or Velcro. Sandals and dress shoes are not recommended since these shoes do not have much room inside to accommodate the orthosis    


Patient physical activity plays a major role in strengthening soft tissues. We strongly recommend having physiotherapy training especially if the patient has associated complications such as hypotonia, ligament laxity, poor balance, and a lack of postural control that cause difficulties in adapting to gravity and the surrounding environment.


Written by:RESHMA IMARATWALE. Physiotherapist

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